Horners are strange people who each have a single horn growing from their foreheads. They live inside a mountain in the Quadling Country.
The Horners are little folks in size, with bodies round as balls and short arms and legs. Their heads are round, too, and they have long pointed ears and a horn set in the middle of the forehead. The horn is not more than six inches long, and is ivory white and sharp pointed. Their skin is light brown, and they wear snow-white robes and walk bare-footed. Their hair is red at the bottom and sometimes hangs over their eyes, then comes a broad circle of yellow hair, and the green hair at the top forms a brush-shaped top-knot. Their leader, Jak Horner, wears a jeweled star in his hair just above his crown.
The Horners are jolly folk and enjoy a good joke. They spend all their time digging radium from the mines under their mountain.
Horner Country is located within a cave so high that it must reach nearly to the top of the mountain within which it lies. It is illuminated by a soft, invisible light. The walls are of dull gray rock and the square houses are made of the same material. The streets of the city are not paved nor has any attempt been made to beautify the houses or their surroundings; the Horners don't see the point since they live on the inside and not the outside.
However, there is nothing grimy or faded about the insides of the houses. They are lined throughout with radium, and the surfaces are highly ornamented with raised designs representing men, animals, flowers, and trees. Soft light radiates from the radium itself and lights the rooms.
The village itself is larger than the neighboring city of the Hoppers. The two countries are separated by a high picket fence of marble which divides the cave into two equal parts.
A war between the Horners and the one-legged Hoppers started when Diksey Horner joked that Hoppers have less understanding. The Patchwork Girl visited them and convinced them to explain the joke and make peace with the Hoppers. Diksey was able to provide Ojo with water from a dark well in his mine, one of the ingredients needed on his quest. (The Patchwork Girl of Oz)
In Dorothy Must Die
The Horners have powerful magic in their horns, so once Dorothy took over Oz, she put out a reward for their capture. According to Nox, there are no more horners left. Annabel was one of the Horners, and she was captured and taken to the Scarecrow's lab. He removed her horn and converted her into a cyborg before she managed to escape. (Dorothy Must Die)